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id="post-info"><h1 class="post-title">异步级联动组件的封装</h1><div id="post-meta"><div class="meta-firstline"><span class="post-meta-date"><i class="far fa-calendar-alt fa-fw post-meta-icon"></i><span class="post-meta-label">发表于</span><time class="post-meta-date-created" datetime="2019-03-09T16:00:00.000Z" title="发表于 2019-03-10 00:00:00">2019-03-10</time><span class="post-meta-separator">|</span><i class="fas fa-history fa-fw post-meta-icon"></i><span class="post-meta-label">更新于</span><time class="post-meta-date-updated" datetime="2019-06-02T16:00:00.000Z" title="更新于 2019-06-03 00:00:00">2019-06-03</time></span><span class="post-meta-categories"><span class="post-meta-separator">|</span><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/%E7%BB%84%E4%BB%B6%E5%B0%81%E8%A3%85/">组件封装</a></span></div><div class="meta-secondline"><span class="post-meta-separator">|</span><span class="post-meta-wordcount"><i class="far fa-file-word fa-fw post-meta-icon"></i><span class="post-meta-label">字数总计:</span><span class="word-count">3.3k</span><span class="post-meta-separator">|</span><i class="far fa-clock fa-fw post-meta-icon"></i><span class="post-meta-label">阅读时长:</span><span>13分钟</span></span><span class="post-meta-separator">|</span><span class="post-meta-pv-cv" id="" data-flag-title="异步级联动组件的封装"><i class="far fa-eye fa-fw post-meta-icon"></i><span class="post-meta-label">阅读量:</span><span id="busuanzi_value_page_pv"></span></span></div></div></div></header><main class="layout" id="content-inner"><div id="post"><article class="post-content" id="article-container"><h1 id="异步的级联动组件"><a href="#异步的级联动组件" class="headerlink" title="异步的级联动组件"></a>异步的级联动组件</h1><h2 id="剖析"><a href="#剖析" class="headerlink" title="剖析"></a>剖析</h2><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>我们上次已经封装了同步的级联动组件 但是数据的格式都是给我们封装好的</span><br><span class="line"><span class="number">2.</span>这次我们来说一下异步的级联动组件</span><br><span class="line"><span class="number">3.</span>数据格式就不是我们上面的数据格式了 而是我们的父级会有ID 然后子级都会有一个字段去标识自己的是属于那个父级的</span><br></pre></td></tr></table></figure>
<p><img src="数据格式1.png" alt=""></p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>这我们以黑龙江举例 可以看出我们的id字段是<span class="number">10</span> 然后我们的pid字段是<span class="number">0</span> 也就是标识这我是最顶级了</span><br></pre></td></tr></table></figure>
<p><img src="数据格式2.png" alt=""></p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>这里我们找到对应父级ID 的自己 可以看出来 这些都是属于黑龙江的 并且每个子集的pid对应的都是父级的ID</span><br><span class="line"><span class="number">2.</span>我们在以哈尔滨举例</span><br></pre></td></tr></table></figure>
<p><img src="数据格式3.png" alt=""></p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>然后我们看到 这就是哈尔滨下里面的子级 对应的是我们哈尔滨的ID字段</span><br><span class="line"><span class="number">2.</span>这就是一个基本上的树结构</span><br><span class="line"><span class="number">3.</span>有的时候这个数据结构需要我们自己的去便利 就要用到深度和广度 也是一个树形数据的最基本算法 下面说到的时候我们回去讲</span><br></pre></td></tr></table></figure>
<h2 id="懒加载基本原理"><a href="#懒加载基本原理" class="headerlink" title="懒加载基本原理"></a>懒加载基本原理</h2><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>上面我们说完了数据格式 下面说说我们要实现的功能</span><br><span class="line"><span class="number">2.</span>首先我们肯定去把最顶级的数据获取到 然后点击每一级的时候 在把他的id传下去 然后去自己里找和这个ID相同的子级 在显示出来</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//第一级别的数据渲染 这里面我们模拟了一个异步的请求</span></span><br><span class="line">&lt;template&gt;</span><br><span class="line">  &lt;div id=<span class="string">&quot;app&quot;</span>&gt;</span><br><span class="line">    &lt;div&gt;&#123;&#123;<span class="built_in">this</span>.value&#125;&#125;&lt;/div&gt;</span><br><span class="line">    &lt;Cascader :options=<span class="string">&quot;options&quot;</span> v-model=<span class="string">&quot;value&quot;</span>&gt;&lt;/Cascader&gt;</span><br><span class="line">  &lt;/div&gt;</span><br><span class="line">&lt;/template&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line"><span class="keyword">import</span> cityList <span class="keyword">from</span> <span class="string">&#x27;./data.json&#x27;</span></span><br><span class="line"><span class="keyword">import</span> Cascader <span class="keyword">from</span> <span class="string">&#x27;./components/Cascader&#x27;</span></span><br><span class="line"><span class="comment">//这里就是找到当前级别的id 去渲染数据</span></span><br><span class="line"><span class="keyword">const</span> citryfilter = <span class="function">(<span class="params">pid</span>) =&gt;</span> &#123;</span><br><span class="line">  <span class="keyword">return</span> <span class="keyword">new</span> <span class="built_in">Promise</span>(<span class="function">(<span class="params">resolve, reject</span>) =&gt;</span> &#123;</span><br><span class="line">    <span class="built_in">setTimeout</span>(<span class="function">() =&gt;</span> &#123;</span><br><span class="line">      resolve(cityList.filter(<span class="function"><span class="params">item</span> =&gt;</span> item.pid === pid))</span><br><span class="line">    &#125;, <span class="number">1000</span>)</span><br><span class="line">  &#125;)</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> &#123;</span><br><span class="line">  name: <span class="string">&#x27;App&#x27;</span>,</span><br><span class="line">  components: &#123;</span><br><span class="line">    Cascader</span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="keyword">async</span> mounted () &#123;</span><br><span class="line">    <span class="built_in">this</span>.options = <span class="keyword">await</span> citryfilter(<span class="string">&#x27;0&#x27;</span>)</span><br><span class="line">    <span class="built_in">console</span>.log(<span class="built_in">this</span>.options)</span><br><span class="line">  &#125;,</span><br><span class="line">  data () &#123;</span><br><span class="line">    <span class="keyword">return</span> &#123;</span><br><span class="line">      value: [],</span><br><span class="line">      options: [</span><br><span class="line"></span><br><span class="line">      ]</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br><span class="line">&lt;/script&gt;</span><br></pre></td></tr></table></figure>
<p><img src="第一级别的数据.gif" alt=""></p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>现在我们已经拿到第一级别的数据了 当我们点击的时候就能拿到当前点击的是哪一项</span><br><span class="line"><span class="number">2.</span>然后在去把当前点击的id传过去 获取到他的孩子</span><br><span class="line"><span class="number">3.</span>这里需要注意的时候 我们每次在选择的时候会把当前点击的下一个子级删除 参考同步的级联动组件 所以我们每次点击的时候应该去拿我们最后一项 才是你当前的点击的项</span><br><span class="line"><span class="number">4.</span>这个步骤是在 CascaderItem.vue 递归组件里完成 我们当时是向上传值 虽然我们已经绑定了v-model 但是这里我们需要把当前的点击项目赋值 所以还要监听input事件 去写逻辑</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//CascaderItem.vue组件 这里有我们当前点击的方法</span></span><br><span class="line">select (item) &#123;</span><br><span class="line">      <span class="built_in">this</span>.currentSelected = item</span><br><span class="line">      <span class="comment">// 因为子组件不能改变父组件的值 所以我们需要深拷贝一下</span></span><br><span class="line">      <span class="keyword">const</span> cloneValue = <span class="built_in">JSON</span>.parse(<span class="built_in">JSON</span>.stringify(<span class="built_in">this</span>.value))</span><br><span class="line">      <span class="comment">// 当点击的第二级别的时候删除自己下一级别的所有数据</span></span><br><span class="line">      cloneValue.splice(<span class="built_in">this</span>.level + <span class="number">1</span>)</span><br><span class="line">      <span class="comment">// 这里我们的level是每次都会加一的 然后让我们数组的每一位对应数据每一级的值</span></span><br><span class="line">      cloneValue[<span class="built_in">this</span>.level] = item</span><br><span class="line">      <span class="comment">// 选择好的值以后 我们需要向上传递</span></span><br><span class="line">      <span class="built_in">this</span>.$emit(<span class="string">&#x27;change&#x27;</span>, cloneValue)</span><br><span class="line">    &#125;</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//中间层组件 绑定了自己定事件 是最底层组件向上传递的值</span></span><br><span class="line">&lt;template&gt;</span><br><span class="line">  &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;cascader&quot;</span> v-click-outside=<span class="string">&quot;close&quot;</span>&gt;</span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;title&quot;</span> @click=<span class="string">&quot;toggle&quot;</span>&gt;</span><br><span class="line">      &#123;&#123;result&#125;&#125;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">    &lt;div v-<span class="keyword">if</span>=<span class="string">&quot;isVisbel&quot;</span>&gt;</span><br><span class="line">        &lt;Cascader-item :options=<span class="string">&quot;options&quot;</span> :value=<span class="string">&quot;value&quot;</span> :level=<span class="string">&quot;0&quot;</span> @change=<span class="string">&quot;change&quot;</span>&gt;&lt;/Cascader-item&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">  &lt;/div&gt;</span><br><span class="line">&lt;/template&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line"><span class="keyword">import</span> clickOutside <span class="keyword">from</span> <span class="string">&#x27;./clickOutside&#x27;</span></span><br><span class="line"><span class="keyword">import</span> CascaderItem <span class="keyword">from</span> <span class="string">&#x27;./CascaderItem&#x27;</span></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> &#123;</span><br><span class="line">  components: &#123;</span><br><span class="line">    CascaderItem</span><br><span class="line">  &#125;,</span><br><span class="line">  directives: &#123;</span><br><span class="line">    clickOutside</span><br><span class="line">  &#125;,</span><br><span class="line">  computed: &#123;</span><br><span class="line">    result () &#123;</span><br><span class="line">      <span class="keyword">return</span> <span class="built_in">this</span>.value.map(<span class="function"><span class="params">item</span> =&gt;</span> item.label).join(<span class="string">&#x27;/&#x27;</span>)</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  props: &#123;</span><br><span class="line">    value: &#123;</span><br><span class="line">      type: <span class="built_in">Array</span>,</span><br><span class="line">      <span class="keyword">default</span>: <span class="function">() =&gt;</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> []</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">    options: &#123;</span><br><span class="line">      type: <span class="built_in">Array</span>,</span><br><span class="line">      <span class="keyword">default</span>: <span class="function">() =&gt;</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> []</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  data () &#123;</span><br><span class="line">    <span class="keyword">return</span> &#123;</span><br><span class="line">    <span class="comment">// 用来存放我们文本框显示的值</span></span><br><span class="line"></span><br><span class="line">      isVisbel: <span class="literal">false</span></span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line"></span><br><span class="line">  methods: &#123;</span><br><span class="line">    <span class="comment">// 从组件接收过来的值 然后在向上传递</span></span><br><span class="line">    change (value) &#123;</span><br><span class="line">      <span class="comment">//触发了上层组件的input事件  </span></span><br><span class="line">      <span class="built_in">this</span>.$emit(<span class="string">&#x27;input&#x27;</span>, value)</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="comment">// 点击外面的时候关闭显示内容</span></span><br><span class="line">    close () &#123;</span><br><span class="line">      <span class="built_in">this</span>.isVisbel = <span class="literal">false</span></span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="comment">// 切换隐藏于显示</span></span><br><span class="line">    toggle () &#123;</span><br><span class="line">      <span class="built_in">this</span>.isVisbel = !<span class="built_in">this</span>.isVisbel</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line">&lt;/script&gt;</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//上层组件</span></span><br><span class="line">&lt;template&gt;</span><br><span class="line">  &lt;div id=<span class="string">&quot;app&quot;</span>&gt;</span><br><span class="line">    &lt;div&gt;&#123;&#123;<span class="built_in">this</span>.value&#125;&#125;&lt;/div&gt;</span><br><span class="line">    &lt;Cascader :options=<span class="string">&quot;options&quot;</span> v-model=<span class="string">&quot;value&quot;</span> @input=<span class="string">&quot;input&quot;</span>&gt;&lt;/Cascader&gt;</span><br><span class="line">  &lt;/div&gt;</span><br><span class="line">&lt;/template&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line"><span class="keyword">import</span> cityList <span class="keyword">from</span> <span class="string">&#x27;./data.json&#x27;</span></span><br><span class="line"><span class="keyword">import</span> Cascader <span class="keyword">from</span> <span class="string">&#x27;./components/Cascader&#x27;</span></span><br><span class="line"><span class="keyword">const</span> citryfilter = <span class="function">(<span class="params">pid</span>) =&gt;</span> &#123;</span><br><span class="line">  <span class="keyword">return</span> <span class="keyword">new</span> <span class="built_in">Promise</span>(<span class="function">(<span class="params">resolve, reject</span>) =&gt;</span> &#123;</span><br><span class="line">    <span class="built_in">setTimeout</span>(<span class="function">() =&gt;</span> &#123;</span><br><span class="line">      resolve(cityList.filter(<span class="function"><span class="params">item</span> =&gt;</span> item.pid === pid))</span><br><span class="line">    &#125;, <span class="number">1000</span>)</span><br><span class="line">  &#125;)</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> &#123;</span><br><span class="line">  name: <span class="string">&#x27;App&#x27;</span>,</span><br><span class="line">  components: &#123;</span><br><span class="line">    Cascader</span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="keyword">async</span> mounted () &#123;</span><br><span class="line">    <span class="built_in">this</span>.options = <span class="keyword">await</span> citryfilter(<span class="string">&#x27;0&#x27;</span>)</span><br><span class="line">  &#125;,</span><br><span class="line">  data () &#123;</span><br><span class="line">    <span class="keyword">return</span> &#123;</span><br><span class="line">      value: [],</span><br><span class="line">      options: [</span><br><span class="line"></span><br><span class="line">      ],</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  methods: &#123;</span><br><span class="line">    <span class="comment">//监听了最下层组件传递过来的值 并且保存了一下  </span></span><br><span class="line">    input (value) &#123;</span><br><span class="line">    <span class="comment">//这里注意我们在最底层组件的时候是把当前项目的最后一层删了 所以我们只拿数组的最后一个就可以 就是当前的点击项目 </span></span><br><span class="line">      <span class="keyword">let</span> currentItem = value[value.length - <span class="number">1</span>]</span><br><span class="line">      <span class="built_in">console</span>.log(<span class="built_in">this</span>.currentItem, <span class="string">&#x27;----当前点击的项&#x27;</span>)</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line">&lt;/script&gt;</span><br></pre></td></tr></table></figure>
<p><img src="拿到当前点击项.gif" alt=""></p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>上面我们已经可以已经可以拿到当前的项 然后我们把当前的ID传过去在获取一下当前的子级</span><br><span class="line"><span class="number">2.</span>拿到当前子级了 我们在把数据插入进入即可</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br></pre></td><td class="code"><pre><span class="line">&lt;template&gt;</span><br><span class="line">  &lt;div id=<span class="string">&quot;app&quot;</span>&gt;</span><br><span class="line">    &lt;div&gt;&#123;&#123;<span class="built_in">this</span>.value&#125;&#125;&lt;/div&gt;</span><br><span class="line">    &lt;Cascader :options=<span class="string">&quot;options&quot;</span> v-model=<span class="string">&quot;value&quot;</span> @input=<span class="string">&quot;input&quot;</span>&gt;&lt;/Cascader&gt;</span><br><span class="line">  &lt;/div&gt;</span><br><span class="line">&lt;/template&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line"><span class="keyword">import</span> cityList <span class="keyword">from</span> <span class="string">&#x27;./data.json&#x27;</span></span><br><span class="line"><span class="keyword">import</span> Cascader <span class="keyword">from</span> <span class="string">&#x27;./components/Cascader&#x27;</span></span><br><span class="line"><span class="keyword">const</span> citryfilter = <span class="function">(<span class="params">pid</span>) =&gt;</span> &#123;</span><br><span class="line">  <span class="keyword">return</span> <span class="keyword">new</span> <span class="built_in">Promise</span>(<span class="function">(<span class="params">resolve, reject</span>) =&gt;</span> &#123;</span><br><span class="line">    <span class="built_in">setTimeout</span>(<span class="function">() =&gt;</span> &#123;</span><br><span class="line">      resolve(cityList.filter(<span class="function"><span class="params">item</span> =&gt;</span> item.pid === pid))</span><br><span class="line">    &#125;, <span class="number">1000</span>)</span><br><span class="line">  &#125;)</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> &#123;</span><br><span class="line">  name: <span class="string">&#x27;App&#x27;</span>,</span><br><span class="line">  components: &#123;</span><br><span class="line">    Cascader</span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="keyword">async</span> mounted () &#123;</span><br><span class="line">    <span class="built_in">this</span>.options = <span class="keyword">await</span> citryfilter(<span class="string">&#x27;0&#x27;</span>)</span><br><span class="line">  &#125;,</span><br><span class="line">  data () &#123;</span><br><span class="line">    <span class="keyword">return</span> &#123;</span><br><span class="line">      value: [],</span><br><span class="line">      options: [</span><br><span class="line"></span><br><span class="line">      ],</span><br><span class="line">      currentItem: <span class="literal">null</span></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  methods: &#123;</span><br><span class="line">    <span class="keyword">async</span> input (value) &#123;</span><br><span class="line">      <span class="comment">//拿到当前的点击项  </span></span><br><span class="line">      <span class="keyword">const</span> currentItem = value[value.length - <span class="number">1</span>]</span><br><span class="line">      <span class="comment">//去获取孩子</span></span><br><span class="line">      <span class="keyword">const</span> children = <span class="keyword">await</span> citryfilter(currentItem.id)</span><br><span class="line">      <span class="comment">//这里原本我们的 currentItem 数据最开始 是没有 children的这个键名 你动态的去添加的 所以去需要用$set</span></span><br><span class="line">      <span class="built_in">this</span>.$set(currentItem, <span class="string">&#x27;children&#x27;</span>, children)</span><br><span class="line">      <span class="comment">//这里为什么没有在options里数据在去添加呢 因为你用v-model双向数据绑定了 会继续向下传值 而且我们的视图也是	 根据你的value去渲染的</span></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line">&lt;/script&gt;</span><br></pre></td></tr></table></figure>
<h2 id="封装"><a href="#封装" class="headerlink" title="封装"></a>封装</h2><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>上面基本上就是懒加载的原理 但是对于用户而言是比较痛苦的 </span><br><span class="line"><span class="number">2.</span>所以我们要继续封装 让用户给组件传递一个函数 形参有id 和 回调函数(用来传递你刚才获取点击的下一个子级)</span><br><span class="line"><span class="number">3.</span>然后我们在组件内部去完成懒加载的原理即可</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//外层组件</span></span><br><span class="line">&lt;template&gt;</span><br><span class="line">  &lt;div id=<span class="string">&quot;app&quot;</span>&gt;</span><br><span class="line">    &lt;div&gt;&#123;&#123;<span class="built_in">this</span>.options&#125;&#125;&lt;/div&gt;</span><br><span class="line">    &lt;Cascader :options.sync=<span class="string">&quot;options&quot;</span> v-model=<span class="string">&quot;value&quot;</span> :lazyload=<span class="string">&quot;lazyload&quot;</span>&gt;&lt;/Cascader&gt;</span><br><span class="line">  &lt;/div&gt;</span><br><span class="line">&lt;/template&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line"><span class="keyword">import</span> cityList <span class="keyword">from</span> <span class="string">&#x27;./data.json&#x27;</span></span><br><span class="line"><span class="keyword">import</span> Cascader <span class="keyword">from</span> <span class="string">&#x27;./components/Cascader&#x27;</span></span><br><span class="line"><span class="keyword">const</span> citryfilter = <span class="function">(<span class="params">pid</span>) =&gt;</span> &#123;</span><br><span class="line">  <span class="keyword">return</span> <span class="keyword">new</span> <span class="built_in">Promise</span>(<span class="function">(<span class="params">resolve, reject</span>) =&gt;</span> &#123;</span><br><span class="line">    <span class="built_in">setTimeout</span>(<span class="function">() =&gt;</span> &#123;</span><br><span class="line">      resolve(cityList.filter(<span class="function"><span class="params">item</span> =&gt;</span> item.pid === pid))</span><br><span class="line">    &#125;, <span class="number">1000</span>)</span><br><span class="line">  &#125;)</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> &#123;</span><br><span class="line">  name: <span class="string">&#x27;App&#x27;</span>,</span><br><span class="line">  components: &#123;</span><br><span class="line">    Cascader</span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="keyword">async</span> mounted () &#123;</span><br><span class="line">    <span class="built_in">this</span>.options = <span class="keyword">await</span> citryfilter(<span class="string">&#x27;0&#x27;</span>)</span><br><span class="line">  &#125;,</span><br><span class="line">  data () &#123;</span><br><span class="line">    <span class="keyword">return</span> &#123;</span><br><span class="line">      value: [],</span><br><span class="line">      options: [</span><br><span class="line"></span><br><span class="line">      ],</span><br><span class="line">      currentItem: <span class="literal">null</span></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  methods: &#123;</span><br><span class="line">    <span class="comment">// 这里我们传进去一个函数 为了能在组件内部调用外面的这个函数 然后通过回调的形式把我查出来的孩子在通过回调传入进去</span></span><br><span class="line">    <span class="comment">// 有了孩子在去更新视图</span></span><br><span class="line">    <span class="comment">//id是我们子组件去完成的 因为在子组件里我们才会触发点击事件能拿到当前项目的ID  </span></span><br><span class="line">    <span class="keyword">async</span> lazyload (id, callback) &#123;</span><br><span class="line">      <span class="comment">//根据id去查找孩子   </span></span><br><span class="line">      <span class="keyword">const</span> children = <span class="keyword">await</span> citryfilter(id)</span><br><span class="line">      <span class="comment">//然后在把孩子传递给我们的子组件</span></span><br><span class="line">      callback(children)</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line">&lt;/script&gt;</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//子组件</span></span><br><span class="line"><span class="comment">/* eslint-disable no-cond-assign */</span></span><br><span class="line">&lt;template&gt;</span><br><span class="line">  &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;cascader&quot;</span> v-click-outside=<span class="string">&quot;close&quot;</span>&gt;</span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;title&quot;</span> @click=<span class="string">&quot;toggle&quot;</span>&gt;</span><br><span class="line">      &#123;&#123;result&#125;&#125;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">    &lt;div v-<span class="keyword">if</span>=<span class="string">&quot;isVisbel&quot;</span>&gt;</span><br><span class="line">        &lt;Cascader-item :options=<span class="string">&quot;options&quot;</span> :value=<span class="string">&quot;value&quot;</span> :level=<span class="string">&quot;0&quot;</span> @change=<span class="string">&quot;change&quot;</span>&gt;&lt;/Cascader-item&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">  &lt;/div&gt;</span><br><span class="line">&lt;/template&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line"><span class="keyword">import</span> clickOutside <span class="keyword">from</span> <span class="string">&#x27;./clickOutside&#x27;</span></span><br><span class="line"><span class="keyword">import</span> CascaderItem <span class="keyword">from</span> <span class="string">&#x27;./CascaderItem&#x27;</span></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> &#123;</span><br><span class="line">  components: &#123;</span><br><span class="line">    CascaderItem</span><br><span class="line">  &#125;,</span><br><span class="line">  directives: &#123;</span><br><span class="line">    clickOutside</span><br><span class="line">  &#125;,</span><br><span class="line">  computed: &#123;</span><br><span class="line">    result () &#123;</span><br><span class="line">      <span class="keyword">return</span> <span class="built_in">this</span>.value.map(<span class="function"><span class="params">item</span> =&gt;</span> item.label).join(<span class="string">&#x27;/&#x27;</span>)</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  props: &#123;</span><br><span class="line">    lazyload: &#123;</span><br><span class="line">      type: <span class="built_in">Function</span></span><br><span class="line">    &#125;,</span><br><span class="line">    value: &#123;</span><br><span class="line">      type: <span class="built_in">Array</span>,</span><br><span class="line">      <span class="keyword">default</span>: <span class="function">() =&gt;</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> []</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">    options: &#123;</span><br><span class="line">      type: <span class="built_in">Array</span>,</span><br><span class="line">      <span class="keyword">default</span>: <span class="function">() =&gt;</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> []</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  data () &#123;</span><br><span class="line">    <span class="keyword">return</span> &#123;</span><br><span class="line">    <span class="comment">// 用来存放我们文本框显示的值</span></span><br><span class="line"></span><br><span class="line">      isVisbel: <span class="literal">false</span></span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line"></span><br><span class="line">  methods: &#123;</span><br><span class="line">    <span class="comment">//ps:这里为什么要用二叉查找 因为我们目前只看到了第一项 但是如果层级多了 你不知道你点击的那项对应的children是哪一项 当然你也可以写递归 不过性能会差很多  </span></span><br><span class="line">    <span class="comment">//6.这里我们用到树的算法 详情见树的算法 这里我们采用的是广度查找 就也就是二叉查找原理详见树的算法  </span></span><br><span class="line">    handle (id, children) &#123;</span><br><span class="line">      <span class="comment">// 由于子组件不能更改父组件传递过来的数据 所以要深度拷贝一份</span></span><br><span class="line">      <span class="keyword">const</span> cloneOptions = <span class="built_in">JSON</span>.parse(<span class="built_in">JSON</span>.stringify(<span class="built_in">this</span>.options))</span><br><span class="line">      <span class="comment">//把我们的父组件传递过来的数据克隆一下 放在一个栈中</span></span><br><span class="line">      <span class="keyword">let</span> stack = [...cloneOptions]</span><br><span class="line">      <span class="comment">//开始从这个栈中的第一个项开始查找</span></span><br><span class="line">      <span class="keyword">let</span> index = <span class="number">0</span></span><br><span class="line">      <span class="comment">//当前的的查找的值</span></span><br><span class="line">      <span class="keyword">let</span> current</span><br><span class="line">      <span class="comment">// 开始循环 把我们的数组的第零项先拿出来 赋值给我们的当前项</span></span><br><span class="line">      <span class="keyword">while</span> ((current = stack[index++])) &#123;</span><br><span class="line">        <span class="comment">// 看看当前的项是不是我们点击的那一项 如果不是我们就再把他children放在栈中</span></span><br><span class="line">        <span class="keyword">if</span> (current.id !== id) &#123;</span><br><span class="line">          <span class="keyword">if</span> (current.children) &#123;</span><br><span class="line">            stack = stack.concat(current.children)</span><br><span class="line">          &#125;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">          <span class="comment">// 这里就是找到了</span></span><br><span class="line">          <span class="keyword">break</span></span><br><span class="line">        &#125;</span><br><span class="line">      &#125;</span><br><span class="line">      <span class="keyword">if</span> (current) &#123;</span><br><span class="line">        <span class="comment">// 就把我们当前项目赋值</span></span><br><span class="line">        current.children = children</span><br><span class="line">        <span class="comment">// 然后在更新给父组件 父组件别忘了加sync</span></span><br><span class="line">        <span class="built_in">this</span>.$emit(<span class="string">&#x27;update:options&#x27;</span>, cloneOptions)</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="comment">// 从组件接收过来的值 然后在向上传递</span></span><br><span class="line">    change (value) &#123;</span><br><span class="line">      <span class="comment">//1.拿到了当前点击项目的ID  </span></span><br><span class="line">      <span class="keyword">const</span> id = value[value.length - <span class="number">1</span>].id</span><br><span class="line">      <span class="comment">//2.如果你给我传lazyload功能了我就去用</span></span><br><span class="line">      <span class="keyword">if</span> (<span class="built_in">this</span>.lazyload) &#123; </span><br><span class="line">        <span class="comment">//3.把id传递给了我们的  </span></span><br><span class="line">        <span class="built_in">this</span>.lazyload(id, <span class="function">(<span class="params">children</span>) =&gt;</span> &#123;</span><br><span class="line">          <span class="comment">//4.找到孩子以后我们这里需要知道把孩子插入到对应的父级  </span></span><br><span class="line">          <span class="built_in">this</span>.handle(id, children)</span><br><span class="line">        &#125;)</span><br><span class="line">      &#125;</span><br><span class="line">      <span class="built_in">this</span>.$emit(<span class="string">&#x27;input&#x27;</span>, value)</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="comment">// 点击外面的时候关闭显示内容</span></span><br><span class="line">    close () &#123;</span><br><span class="line">      <span class="built_in">this</span>.isVisbel = <span class="literal">false</span></span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="comment">// 切换隐藏于显示</span></span><br><span class="line">    toggle () &#123;</span><br><span class="line">      <span class="built_in">this</span>.isVisbel = !<span class="built_in">this</span>.isVisbel</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line">&lt;/script&gt;</span><br></pre></td></tr></table></figure>
<p><img src="树的查找.gif" alt=""></p>
<h2 id="视图更新"><a href="#视图更新" class="headerlink" title="视图更新"></a>视图更新</h2><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1.</span>通过上面的代码我们可以看出 我们查找出来的数据孩子已经插入到我们对应的父级当中了 但是视图没有更新</span><br><span class="line"><span class="number">2.</span>我们知道我们的视图更新是跟我们的value关联的</span><br><span class="line"><span class="number">3.</span>所以这里我么的options更新的时候 还要通知一下我们的视图更新也就是需要 在我们的计算属性里重新写一下</span><br></pre></td></tr></table></figure>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//最里层组件</span></span><br><span class="line">&lt;template&gt;</span><br><span class="line">  &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;content&quot;</span>&gt;</span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;content-left&quot;</span>&gt;</span><br><span class="line">        &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;label&quot;</span> v-<span class="keyword">for</span>=<span class="string">&quot;(item,index) in options&quot;</span> :key=<span class="string">&quot;index&quot;</span> @click=<span class="string">&quot;select(item)&quot;</span>&gt;</span><br><span class="line">            &#123;&#123;item.label&#125;&#125;</span><br><span class="line">        &lt;/div&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">&quot;content-right&quot;</span> v-<span class="keyword">if</span>=<span class="string">&quot;lists &amp;&amp; lists.length&quot;</span>&gt;</span><br><span class="line">       &lt;Cascader-item :options=<span class="string">&quot;lists&quot;</span>  :level=<span class="string">&quot;level+1&quot;</span> @change=<span class="string">&quot;change&quot;</span> :value=<span class="string">&quot;value&quot;</span>&gt;&lt;/Cascader-item&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">  &lt;/div&gt;</span><br><span class="line">&lt;/template&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> &#123;</span><br><span class="line">  name: <span class="string">&#x27;CascaderItem&#x27;</span>,</span><br><span class="line">  props: &#123;</span><br><span class="line">    level: &#123;</span><br><span class="line">      type: <span class="built_in">Number</span></span><br><span class="line">    &#125;,</span><br><span class="line">    value: &#123;</span><br><span class="line">      type: <span class="built_in">Array</span>,</span><br><span class="line">      <span class="keyword">default</span>: <span class="function">() =&gt;</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> []</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">    options: &#123;</span><br><span class="line">      type: <span class="built_in">Array</span>,</span><br><span class="line">      <span class="keyword">default</span>: <span class="function">() =&gt;</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> []</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  data () &#123;</span><br><span class="line">    <span class="keyword">return</span> &#123;</span><br><span class="line">      currentSelected: <span class="literal">null</span></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  computed: &#123;</span><br><span class="line">    lists () &#123;</span><br><span class="line">      <span class="comment">//这里的options是我们最外层组件传递过来的 是最新的数据 所以我们要去查找一下 注意这里的option只是我们当前点击的那一项   </span></span><br><span class="line">      <span class="keyword">const</span> o = <span class="built_in">this</span>.options.find(<span class="function"><span class="params">item</span> =&gt;</span> item.id === <span class="built_in">this</span>.value[<span class="built_in">this</span>.level].id)</span><br><span class="line">      <span class="keyword">return</span> o.children</span><br><span class="line">      <span class="comment">// return this.value[this.level] &amp;&amp; this.value[this.level].children</span></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;,</span><br><span class="line">  methods: &#123;</span><br><span class="line">    change (item) &#123;</span><br><span class="line">      <span class="built_in">this</span>.$emit(<span class="string">&#x27;change&#x27;</span>, item)</span><br><span class="line">    &#125;,</span><br><span class="line">    select (item) &#123;</span><br><span class="line">      <span class="built_in">this</span>.currentSelected = item</span><br><span class="line">      <span class="comment">// 因为子组件不能改变父组件的值 所以我们需要深拷贝一下</span></span><br><span class="line">      <span class="keyword">const</span> cloneValue = <span class="built_in">JSON</span>.parse(<span class="built_in">JSON</span>.stringify(<span class="built_in">this</span>.value))</span><br><span class="line">      <span class="comment">// 当点击的第二级别的时候删除自己下一级别的所有数据</span></span><br><span class="line">      cloneValue.splice(<span class="built_in">this</span>.level + <span class="number">1</span>)</span><br><span class="line">      <span class="comment">// 这里我们的level是每次都会加一的 然后让我们数组的每一位对应数据每一级的值</span></span><br><span class="line">      cloneValue[<span class="built_in">this</span>.level] = item</span><br><span class="line">      <span class="comment">// 选择好的值以后 我们需要向上传递</span></span><br><span class="line">      <span class="built_in">this</span>.$emit(<span class="string">&#x27;change&#x27;</span>, cloneValue)</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><img src="懒加载完成.gif" alt=""></p>
<h2 id=""><a href="#" class="headerlink" title=" "></a> </h2></article><div class="post-copyright"><div class="post-copyright__title"><span class="post-copyright-info"><h>异步级联动组件的封装</h></span></div><div class="post-copyright__type"><span class="post-copyright-info"><a href="http://example.com/2019/03/10/%E5%BC%82%E6%AD%A5%E7%9A%84%E7%BA%A7%E8%81%94%E5%8A%A8%E7%BB%84%E4%BB%B6/">http://example.com/2019/03/10/%E5%BC%82%E6%AD%A5%E7%9A%84%E7%BA%A7%E8%81%94%E5%8A%A8%E7%BB%84%E4%BB%B6/</a></span></div><div class="post-copyright-m"><div class="post-copyright-m-info"><div class="post-copyright-a"><h>作者</h><div class="post-copyright-cc-info"><h>北城韩雨</h></div></div><div class="post-copyright-c"><h>发布于</h><div class="post-copyright-cc-info"><h>2019-03-10</h></div></div><div class="post-copyright-u"><h>更新于</h><div class="post-copyright-cc-info"><h>2019-06-03</h></div></div><div class="post-copyright-c"><h>许可协议</h><div class="post-copyright-cc-info"><a class="icon" rel="noopener" target="_blank" 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<p style="background:rgba(255,255,255,1);margin:0"> <img src="/img/code.png"></img> </p></div></div><div class="sticky_layout"><div class="card-widget" id="card-toc"><div class="item-headline"><i class="fas fa-stream"></i><span>目录</span></div><div class="toc-content"><ol class="toc"><li class="toc-item toc-level-1"><a class="toc-link" href="#%E5%BC%82%E6%AD%A5%E7%9A%84%E7%BA%A7%E8%81%94%E5%8A%A8%E7%BB%84%E4%BB%B6"><span class="toc-text">异步的级联动组件</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E5%89%96%E6%9E%90"><span class="toc-text">剖析</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E6%87%92%E5%8A%A0%E8%BD%BD%E5%9F%BA%E6%9C%AC%E5%8E%9F%E7%90%86"><span class="toc-text">懒加载基本原理</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E5%B0%81%E8%A3%85"><span class="toc-text">封装</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%A7%86%E5%9B%BE%E6%9B%B4%E6%96%B0"><span 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